Isolation, purification and identification of the compound or compounds responsible for sperm chemotaxis prior to fertilization in the marine hydroid, Tubularia. Studies of possible mechanisms of sperm reorientation during chemotaxis, particularly the effects of the absence of environmental calcium ion will also be undertaken. Further work into the description of sperm chemotaxis in the solitary tunicates Ciona and Styela will be performed, particularly with regard to the nature of the sperm attractant in these species.